General zoology and entomology Grassi's earlier works were on
anatomy and then
entomology. He studied the development of the
vertebral column in
bony fishes and also endemic
goiter. The arrow worms were later classified as a separate phylum Chaetognatha, and are recognised as "enigmatic" animals. His associate Salvatore Calandruccio collected an unusual spider from
Mount Etna in Sicily. Grassi identified it as not only new species but as belonging to a new family, and gave the name,
Koenenia mirabilis in 1885, dedicated to his wife. He also made significant contribution to the study of the phylloxera of grapes, which he pursued for several years. The notes of his observations
La questione fillosserica in Italia (1904) influenced the Italian Ministry of Agriculture, which eventually requested him to do an exhaustive study of this subject. In 1912 he produced a monumental investigation of the
morphology and biology of the Italian and other European genera of phylloxera. It was a foundation for systematic control of agricultural pests. After twenty-two days, he found fresh eggs in his faeces. Thus proving that the roundworm is transmitted through direct
ingestion from contaminated source. In 1879, Grassi became the first to identify protozoans similar to amoebas from the human excreta. He gave a vivid description of the then named
Amoeba coli, later classified as
Entamoeba coli, which he considered to be harmless parasites as he found them from both sick and heathy individuals. At the time, these protozoans were believed to be pathogenic parasites like other amoebas. and closely related to the pathogenic species,
E. histolytica. His report in 1885 showed the role of commensal protozoans in the digestion process of food in termites. and later found to infect humans as well.
Malariology Discovery of malarial parasites Grassi started to study malaria in 1888 while at the University of Catania, with a colleague
Raimondo Feletti. Laveran gave the name
Oscillaria malariae, which was ultimately changed to
Plasmodium falciparum by the
International Commission on Zoological Nomenclature (ICZN) in 1954. Grassi and Feletti made the second discovery the next year that the harmless form of malaria was caused by a very similar protozoan which they named
Laverania malariae (the genus name honouring Laveran)
. They reported the discovery in the December issue of
Riforma Medica as "
Sui Parasiti della Malaria" (On the Parasite of Malaria). The sequel report in 1890 described the discovery of the third human malarial parasite which they called
Haemamoeba vivax. Along with the new description indicating obvious relationship between the two parasite, they reclassified
Laverania malariae into
Haemamoeba and renamed it
H. malariae. In 1891, Grassi performed the first
inoculation of malaria parasites from one bird into another. Grassi reused the genus
Laverania for
O. malariae (unbeknown to Laveran,
Oscillaria was already a scientific name for other protists). (The full report was published in September 1898.) In Ross's case the experiment was an infection of bird malaria in sparrows from the bite of what he called "grey" mosquitos. Upon the news, Grassi knew that it was important to test the possibility of human infection from mosquitos. In September, on his way back to Rome, he collected mosquitos some of which he could identify as
Anopheles. When the blood-fed mosquitos were dissected after few days, several developmental stages of the parasite were visible inside the mosquito. The most important observation was oocysts (from which human infective forms, sporozoa, would eventually emerge) that indicated the successful growth of the parasite in the mosquitos. Grassi, Bignami and Bastianelli reported the discovery to the
Accademia dei Lincei on 6 November 1898, and was formally read before the meeting of the academy on 4 December. Bignami and Bastianelli published the experiments in the December issue of the
Lancet, Bastianelli especially trying to take majority of the credits in a single-authored report, and explicitly omitting the contributions of Grassi. Grassi published a justification that the main critical experiment was designed and performed by only himself.
Grassi's law Grassi had developed a dogma that "there is no malaria without
Anopheles" or simply, "anophelism without malaria". This was dubbed "Grassi's Law", which is formulated as: infected man + anopheles mosquitoes = malaria. Although the equation is straightforwardly correct, the reverse implication is not so. In many areas, he himself had noted that where anopheline vectors were abundant, malaria was not at all prevalent, and sometimes absent. This caused a little problem in understanding malaria epidemiology for some time. In fact, in 1919 he identified three typical malaria-prevalent localities which were not affected by malaria in the same way: the gardens of Schito near
Naples,
Massarosa in
Tuscany, and Alberone in
Lombardia. The enigma was solved in 1925, soon after his death, by his pupil Falleroni, who demonstrated that there are six
cryptic species, of which only four bite humans and transmit malaria. It was useful but not a great success, as the drug could not prevent the infection. Grassi was among the scientists who advocated the need to eradicate the vector mosquitos to put an end to continued transmission of the parasite. In 1918, he established what he called "malaria observatory" at Fiumicino, where he could monitor the extent of mosquitoes migrating and biting humans in the residential areas. At the time, those who advocated the mosquito eradication method believed that it would be sufficient to control the insect breeding places within the human habitations, such as the marsh area in the case of Fiumicino. In an experiment, Grassi released a group of mosquitoes that he marked with paint. When he looked for the marked mosquitoes after several days, he found that many had strayed and survived in areas more than two miles away from the marsh. It was from this study that the necessity to treat the whole surrounding area of marshland beyond human dwellings was realised. For Fiumicino, Grassi designed an embankment system for the marsh area to prevent mosquito breeding, and that could be utilised for irrigation during summer. The project was initiated but uncompleted at the time of his death. == The 1902 Nobel Prize controversy ==